2,6-Dichloro-9-isopropyl-9H-purine: Properties & Applications
2,6-Dichloro-9-isopropyl-9H-purine: Properties & Applications
2,6-Dichloro-9-isopropyl-9H-purine is a halogenated purine derivative widely employed as a versatile synthetic building block in medicinal chemistry, enabling selective nucleophilic substitution at the C-2 and C-6 positions for the preparation of purine-based bioactive compounds.
- Chemical Name
- 2,6-Dichloro-9-isopropyl-9H-purine
- Molecular Formula
- C8H8Cl2N4
- Molecular Weight
- 231.08 g/mol
- Core Scaffold
- 9-substituted purine (bicyclic pyrimidine-imidazole)
- Key Reactive Sites
- C-2 and C-6 chloro substituents susceptible to nucleophilic aromatic substitution
- N-9 Substituent
- Isopropyl group (protects N-9, prevents unwanted N-alkylation)
- Aladdin SKU
- D175576
Chemical Structure and Properties
2,6-Dichloro-9-isopropyl-9H-purine belongs to the family of 9-substituted purines, featuring the canonical bicyclic purine scaffold composed of a pyrimidine ring fused to an imidazole ring. The two chlorine atoms at positions C-2 and C-6 render the ring system electron-deficient, dramatically activating both sites toward nucleophilic aromatic substitution (SNAr). The isopropyl group at N-9 serves a dual purpose: it locks the regiochemistry of N-substitution (preventing tautomerism and unwanted N-7 alkylation) and modulates the lipophilicity of the molecule, which can be advantageous during purification and in downstream biological studies.
The compound is typically obtained as a white to off-white crystalline solid. Its moderate molecular weight (approximately 231 g/mol) and the presence of two chlorine atoms give it a distinctive isotope pattern readily identifiable by mass spectrometry. The compound is stable under standard laboratory storage conditions when kept dry and away from strong nucleophiles and bases.
Synthesis and Functionalization Strategy
The principal synthetic value of 2,6-Dichloro-9-isopropyl-9H-purine lies in the sequential or selective displacement of its two chloro groups. Because C-6 is generally more electrophilic than C-2 in 2,6-dichloropurines, nucleophiles such as amines, alcohols, and thiols preferentially attack C-6 under mild conditions, allowing stepwise diversification. A second, often harsher set of conditions can then be applied to displace the C-2 chloro group with a different nucleophile, yielding unsymmetrically 2,6-disubstituted purine products.
This orthogonal reactivity makes the compound an excellent scaffold for library synthesis and combinatorial chemistry. Researchers can introduce diverse amine fragments at C-6 first, followed by introduction of oxygen or sulfur nucleophiles at C-2, or vice versa with appropriate selectivity control. Palladium-catalyzed cross-coupling reactions (e.g., Buchwald-Hartwig amination, Suzuki coupling after halogen-metal exchange) have also been reported on related 2,6-dichloropurine substrates, further broadening the structural diversity accessible from this core.
Research and Medicinal Chemistry Applications
Purine derivatives occupy a central place in drug discovery owing to their structural similarity to endogenous purines (adenine, guanine) and their ability to interact with a wide range of biological targets, including kinases, adenosine receptors, phosphodiesterases, and nucleoside-processing enzymes. 2,6-Dichloro-9-isopropyl-9H-purine serves as a direct precursor to N-9-protected purine analogs that can mimic adenosine or hypoxanthine scaffolds after selective functionalization.
In the context of kinase inhibitor research, 2,6-disubstituted purines are well-recognized pharmacophores. The N-9 isopropyl group can also serve as a bioisostere or lipophilicity-tuning element in candidates targeting cyclin-dependent kinases (CDKs), Janus kinases (JAKs), and other therapeutically relevant enzymes. Additionally, this compound is useful in the preparation of purine-based fluorescent probes, chemical biology tools, and functionalized nucleoside analogs for antiviral or anticancer research.
Handling, Storage, and Safety Considerations
As with all halogenated heterocyclic reagents, 2,6-Dichloro-9-isopropyl-9H-purine should be handled with appropriate personal protective equipment (PPE), including nitrile gloves, safety glasses, and a laboratory coat. Operations generating dust or aerosols should be performed in a well-ventilated fume hood. The compound should be kept away from strong nucleophiles, bases, and moisture to prevent premature hydrolysis or substitution of the chloro groups.
For long-term storage, the compound should be kept in a tightly sealed container at room temperature or at 2–8 °C in a cool, dry location protected from light. Users should consult the product-specific Safety Data Sheet (SDS) provided by Aladdin Scientific for detailed hazard classification, first-aid measures, and disposal guidelines before use. Waste containing this compound should be disposed of in accordance with local regulations for halogenated organic waste.
Frequently asked questions
What makes C-6 more reactive than C-2 in 2,6-Dichloro-9-isopropyl-9H-purine toward nucleophiles?
In the purine ring system, C-6 is flanked by N-1 and N-5 (adjacent nitrogens), making it more electron-deficient than C-2 and therefore more susceptible to nucleophilic aromatic substitution under mild conditions. This inherent electronic difference allows chemists to selectively functionalize C-6 first before addressing C-2 under more forcing conditions.
Why is the isopropyl group placed at N-9 rather than N-7 in this purine derivative?
N-9 alkylation is the thermodynamically and kinetically preferred regioisomer in purine chemistry under standard alkylation conditions, and it corresponds to the natural nucleoside linkage position found in biological purines such as adenosine and guanosine. Placing the isopropyl group at N-9 fixes the regiochemistry, prevents tautomerism between N-7 and N-9 forms, and mirrors biologically relevant purine scaffolds, making downstream structure-activity relationship interpretation more straightforward.
How should 2,6-Dichloro-9-isopropyl-9H-purine be stored to maintain stability?
The compound should be stored in a tightly sealed container in a cool, dry, well-ventilated area away from moisture, strong bases, and nucleophiles, ideally at 2–8 °C or room temperature according to the supplier's SDS. Exposure to moisture can promote hydrolysis of the chloro substituents, reducing the compound's synthetic utility over time.
Can 2,6-Dichloro-9-isopropyl-9H-purine be used directly in Pd-catalyzed cross-coupling reactions?
Related 2,6-dichloropurine substrates have been reported to undergo palladium-catalyzed reactions such as Buchwald-Hartwig amination and Suzuki-Miyaura coupling following halogen-metal exchange or borylation. However, the specific scope and conditions for 2,6-Dichloro-9-isopropyl-9H-purine in Pd-catalyzed coupling should be optimized experimentally, as the N-9 isopropyl group and the electronic character of the ring may influence reactivity and selectivity.
References
- Comprehensive Heterocyclic Chemistry (Editors: Katritzky, A. R.; Ramsden, C. A.; Scriven, E. F. V.; Taylor, R. J. K.), Elsevier. Chapter on Purines.
- Legraverend, M.; Grierson, D. S. The purines: A review of synthetic methods and applications in biological systems. Bioorganic & Medicinal Chemistry, 2006.
- Aladdin Scientific Product Page: 2,6-Dichloro-9-isopropyl-9H-purine, SKU D175576.
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